In order to deal with increasing magnetic recording densities, spin-valve type GMR devices are beginning to be put into use. The principle of the spin-valve type GMR devices is explained based on changes in the mean free path of electrons traveling in the direction along the film plane (inplane direction), depending on the angle formed by the magnetization directions of the free layer and the pinned (fixed) layer. The spin-valve type GMR device has achieved a MR ratio (magnetoresistance ratio) of about 10%, which is several times higher than that of conventional anisotropic MR devices.
On the other hand, TMR devices are under development as a material that can provide even higher MR ratios. TMRs utilize the tunnel transition probability that varies with the angle formed by the magnetization directions of two ferromagnetic layers via a non-magnetic tunnel layer. In the TMR devices, unlike the spin-valve type GMRs, current flows in the direction across the film plane (direction perpendicular to the plane).
The following structures of magnetic heads using the TMR devices have been proposed. JP11-213349A discloses a magnetic head having a structure in which a MR device portion of a shield type MR head used in conventional GMR heads is replaced by a TMR device, and a flux guide is provided. JP11-25425A discloses a magnetic head having a structure where a yoke is provided such that the yoke plane is perpendicular to the surface of the substrate, and a TMR device is provided in the yoke. In this magnetic head, the yoke is formed on the substrate, and the magnetoresistive device is provided on a part of the yoke.